We wish to develop a coherent account of the synthesis of polyamines (putrescine, spermidine and spermine) in the mold, Neurospora crassa as a model for this pathway in eucaryotic organisms. Using mutations affecting each step of the pathway, including the key enzyme, ornithine decarboxylase, we will identify with certainty the metabolites which govern the regulation of the path. In addition, mutations of the regulatory elements themselves will be used to dissect the genetic control of the augmentation and inactivation of ornithine decarboxylase. In the course of the metabolic studies, the localization of the sequestered spermidine pool will be refined. With pure ornithine decarboxylase and a polyclonal antibody to it, we shall determine the molecular basis of the augmentation and inactivation of the enzyme. With recombinant DNA techniques, we shall clone the structural gene for ornithine decarboxylase, spe-1, and use it as a probe for the messenger RNA which encodes the enzyme. This will allow us to study the extent to which transcription governs the regulation of ornithine decarboxylase. The results will identify the major elements of regulation in a tractable system. This will aid in clarifying the important, but obscure, relationship of the polyamines to growth and neoplasia in mammalian systems.